Categorizing physically dissimilar stimuli such as objects, words, sounds, and other sensory events into the same class is fundamental to meaning, comprehension, and other aspects of cognitive development and functioning. This application studies fundamental learning processes that underlie stimulus-class formation and the resultant emergence of novel behavior, a characteristic of normal human development that is often deficient and in need of behavioral remediation in individuals with developmental disabilities. The broad objective is to demonstrate that even in the absence of language, establishing particular conditional relations between specific pairs of stimuli via reinforcement versus non-reinforcement yields sets of interchangeable stimuli (viz., stimulus classes) as evidenced by the subsequent ability to respond appropriately to novel, untrained combinations of those stimuli. The project aims are to show how such learning yields well-defined instances of emergent behavior rarely (if ever) seen in non-human animals, rigorously test the predictions of a model which assumes that ordinal position is coded as part of a stimulus'functional characteristics, and test the hypothesis that routinely non-reinforcing certain stimulus combinations while reinforcing other combinations generates stimulus classes containing the elements of the latter. In all of the proposed research, non-verbal animals possessing other, established categorization abilities (pigeons) will be concurrently trained on go/no-go matching tasks in which certain sequences of sample and comparison stimuli end in reinforcement whereas others do not. Later, stimulus-class formation will be tested by presenting novel sequences of those same stimuli. Besides revealing emergent effects, these tests will simultaneously evaluate the ordinal-specific properties of the hypothesized functional stimuli and the importance of continual exposure to non-reinforcement (as well as reinforcement) throughout training. Together, the expected pattern of findings will demonstrate that basic, general learning processes - in particular, the reinforcement contingencies used to establish conditional stimulus relations - can generate stimulus classes even in the absence of language and its neural structures and pathways. PUBLIC HEALTH RELEVANCE: Understanding that disparate things like objects, pictures, and written and spoken words can be related is fundamental to meaning, categorization, language comprehension and other characteristics of normal development and functioning. This application examines basic reinforcement and stimulus control processes that provide a foundation for such understanding and for yielding novel, generative behavior. The project underscores the possible involvement of an unrecognized or easily overlooked feature of stimuli - their temporal or ordinal properties - that may help to explain variation in equivalence training outcomes observed with normal and intellectually disabled populations. Clarifying the nature and influence of these processes is the first step toward the development of comprehensive diagnostic tests and effective treatment interventions for individuals with intellectual impairments. In addition, the discrimination paradigm used in the project has some distinctive advantages over more commonly used behavioral procedures in the developmental disabilities field, thus providing a promising alternative for establishing stimulus classes when other approaches fail.